Customizing IEx for Elixir Nerves target device

UpdatedJune 12, 2021

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Masatoshi Nishiguchi's Blog

62 posts

TL;DR

Find the rootfs_overlay/etc/iex.exs file in your Nerves project directory.

Edit it as you want.

Here is an example.

IO.puts(""" \e[34m████▄▖ \e[36m▐███ \e[34m█▌ ▀▜█▙▄▖ \e[36m▐█ \e[34m█▌ \e[36m▐█▄▖\e[34m▝▀█▌ \e[36m▐█ \e[39mN E R V E S \e[34m█▌ \e[36m▝▀█▙▄▖ ▐█ \e[34m███▌ \e[36m▀▜████\e[0m """) # Add Toolshed helpers to the IEx session use Toolshed if RingLogger in Application.get_env(:logger, :backends, []) do IO.puts(""" RingLogger is collecting log messages from Elixir and Linux. To see the messages, either attach the current IEx session to the logger: RingLogger.attach or print the next messages in the log: RingLogger.next """) end # Print information about the running system IO.puts("") uname # Print information about the connected I2C devices if Code.ensure_loaded?(Circuits.I2C) do IO.puts("") Circuits.I2C.detect_devices() end # Print information about local weather try do IO.puts("") weather() rescue exception -> nil end # Alias some modules to save typing later on alias HelloNerves.Worker

.iex.exs file in Nerves target device

When we make a new Nerves project running the mix nerves.new command, that .iex.exs template is copied into the project's rootfs_overlay/etc directory.

The Nerves logo Ascii art was added in this PR in February 2021 so if you have any Nerves projects that are created before that, you do not see the logo in the IEx. In such a case you can manually paste the Ascii art into your rootfs_overlay/etc/.iex.exs file.

Some use cases

We can do whatever we want in our rootfs_overlay/etc/.iex.exs file, but here are some ideas I came up with.

Print Toolshed functions, such as weather/0, uname/0

Print information about connected I2C devices invoking Circuits.I2C.detect_devices/0.

Aliasing some modules

weather/0 required the Internet connection. Please make sure that :inets is added to extra_application in your mix.exs file.

def application do [ mod: {HelloNerves.Application, []}, extra_applications: [:logger, :runtime_tools, :inets] ] end

That's it!

Customizing IEx for Elixir Nerves target device

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TL;DR

`.iex.exs` file in Elixir

`.iex.exs` file in Nerves target device

Some use cases

Command Palette

More from this blog

TL;DR

.iex.exs file in Elixir

.iex.exs file in Nerves target device

Some use cases

`.iex.exs` file in Elixir

`.iex.exs` file in Nerves target device